Jean-Pierre, As I understand from your description you have a 2.5V output from the dc-dc converter that feeds into an op-amp comparator by using a resistor divider on the + and - inputs to the op-amp. Is this correct? It sounds like a very basic comparator setup. Are you using negative feedback with nothing connected inbetween the output and input of the op-amp? Chris Jakubiec Sun Microsystems ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu